1. Field of the Invention
The present invention relates to stamping presses, and more particularly to a fastener insertion module for inserting a self-clinching fastener into a part being formed on a progressive die within a stamping press.
2. Description of the Prior Art
Known to the steel part stamping industry is the technology of producing parts on a progressive die which is placed within a stamping press. A continuous strip of deformable steel or other material is fed in to the press from which identical parts are to be made. As a given section of the strip passes through the die, it is progressively worked (punched, sheared, formed, etc.) at individual stations so that by the time it reaches the end of the die, it has been formed into a completed part. The completed parts are then sheared off of the strip at the end of the die.
Often, the design of a given part requires that it include one or more self-clinching fasteners or nuts. For example, in the automotive industry, many components of various kinds are attached to metal plates or panels. Self-clinching fasteners are used to attach such parts as, for example, lamps and sheet metal to the vehicle. When such parts are attached, screws or bolts on the part itself are inserted into the threaded hole of the fastener or nut to hold the part in place.
Specialized fasteners known as pierce nuts are commonly used in progressive die stamping presses. A pierce nut first "pierces" the metal strip using a pilot portion on the nut, and then as pressure is applied, it is deformably attached to the strip. A pierce nut requires its own specialized installation tooling that is tailored for use in attaching the given nut known as a die button. A different die button is required for every different pierce nut, and such tooling can be quite elaborate (see, e.g., U.S. Pat. Nos. 5,174,018 and 5,502,888).
Self-clinching fasteners or nuts, as contrasted to pierce nuts, are attached as part of a two-step process. The first step is the punching of the desired hole in the metal part, and the second step is the insertion of the fastener. Historically, the insertion step has been performed on a machine other than the machine which forms the part. The insertion requires a close alignment of the fastener to the punched hole. Insertion forces vary per fastener size, material thickness and composition, but run generally in the range of 2 to 15 tons per fastener.
A progressive die in a stamping press may perform from two to twenty steps during each cycle, and may cycle 30 to 60 times every minute. The total pressure exerted by such presses can easily exceed 500 tons. With so much pressure present, a problem with any one of the many stations of the progressive die may cause an unexpected deformity in the strip passing through the press, and result in damage to the strip, or potentially damage to or destruction of the tooling and the die. Because these dangers are presented by the variables of different fastener sizes, and different material thicknesses and composition, insertion of self-clinching fasteners has not generally been performed on progressive die machines in the past. It is therefore desirable to provide the stamping press with the ability to insert the fastener concurrently with the process of forming the part. Thus, when the part is sheared off at the end of the die, the part is complete.
In addition to the above, the following U.S. patents are also known to exist:
______________________________________ U.S. Pat. No. Issue Date Inventor ______________________________________ 2,325,929 August 3, 1943 Amesbury 4,803,767 February 14, 1989 Obrecht 4,905,362 March 6, 1990 Obrecht 5,174,018 December 29, 1992 Muller 5,189,780 March 2, 1993 Landes 5,502,888 April 2, 1996 Takahashi ______________________________________